1. Field of the Invention
The present invention relates to an improved process for preparing a composition which is capable of imparting stain and soil resistance to installed nylon carpets. More particularly, the invention involves adjusting the pH of an aqueous based (non-solvent) dispersion to a final level of about 4.2 to 4.6. The resulting aqueous (non-solvent) dispersion demonstrates effective freeze-thaw stability.
2. Description of the Related Art
Polyamide substrates, such as nylon carpeting, upholstery fabric, etc. are subject to staining by a variety of agents, such as food and beverages. Those skilled in the art have developed different chemical compounds for making these substrates more stain resistant.
For example, Fitzgerald et al., European Patent Application Publication No. 329,899, discloses treating such polyamide substrates with stain-resistant compositions comprising hydrolyzed ethylenically unsaturated aromatic/maleic anhydride polymers. A copolymer prepared from styrene and maleic anhydride is disclosed as the preferred compound.
These stain-resist, or stain-blocker, agents are distinguished from fluorochemicals which are primarily used to impart soil resistance to textile fibers. Dettre et al., U.S. Pat. No. 4,029,585, discloses applying an aqueous fluorochemical dispersion containing a perfluoroalkyl ester of a carboxylic acid of from 3 to 30 carbon atoms to textile substrates, followed by drying. As a result, the fibers are imparted with a coating that is resistant to dry soiling and does not propagate a flame.
As disclosed in Vinod, U.S. Pat. No. 4,925,707, it is also known to use such fluorochemicals in combination with a stain-blocker agent, such as a hydrolyzed styrene/maleic anhydride copolymer. An aqueous dispersion of the stain and soil-blocking agents may be formed and applied to carpets. More particularly, Vinod discloses applying the composition to a nylon carpet that is installed. This is opposed to immersing the carpet or otherwise treating the precursor nylon polymer or fibers earlier during a manufacturing process.
Conventional fluorochemical dispersions contain solvents, such as 2-butoxyethanol, and isopropyl alcohol, but such solvent-based dispersions, when applied to carpets, may have environmental disadvantages. However, when most aqueous-based (non-solvent) fluorochemical dispersions are stored under freezing conditions and subsequently thawed, they show phase separation, become difficult to apply, and are non-effective. Such freezing conditions may occur during the winter, when the compositions are transported in unheated trucks and stored in unheated areas.
Therefore, it would be desirable to produce an aqueous (non-solvent) dispersion containing a soilblocker fluorochemical dispersion and stain-blocker solution which has effective "freeze-thaw stability." In accordance with this invention, the aqueous dispersion has effective "freeze-thaw stability", if the dispersion doesn't show precipitation, phase separation, or excessive turbidity. The present invention provides an improved process for producing an aqueous dispersion containing an aqueous fluorochemical dispersion and a solution of hydrolyzed styrene/maleic anhydride copolymers. The aqueous based (non-solvent) total dispersion demonstrates effective freeze-thaw stability.